The Four Horsemen (Baron Rivendare)

The actual hero in this battle is Baron Rivendare, but the battle begins with three minions on the enemy's battlefield - the other three horsemen. As long as any of these minions are on the battlefield, Baron Rivendare has immunity. The other three horsemen are: Lady Blaumeux, Thane Korth'azz, and Sir Zeliek. Baron's Hero Power is "Unholy Shadow" which allows him to draw 2 cards for a cost of 5 mana.
In the Heroic Battle, Rivendare has 14 health, and the other three Horsemen are 2/8 minions. The Runeblade is also buffed, with 2 attack, and +6 attack (total 8) if the other three horsemen are dead.

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Acidic Swamp Ooze and silence spells/minions are the key to surviving this battle. Because of the Runeblade, it is much better to leave one silenced horseman on the battlefield, rather than destroy all three of them.

Rivendare will not play any minions other than the horsemen, so his deck is stacked with secrets and spells, making it very tough to keep any minions on the battlefield for very long.

Baron Rivendare has seven health, and the battle begins with the other three horsemen on the battlefield as 1/7 minions, each giving Baron immunity as long as they survive.

Baron's main trick is the "Avenge" spell, which gives a friendly minion +3/+2 when one of his minions dies. So typically once one of the horsemen have been removed, one of the others will get increased attack/health.

The Baron also has the "Runeblade", which is a 1/3 weapon for 3 mana cost, that has +3 attack if the other horsemen are dead.